Heavy doors, such as those used on walk-in refrigerators, are often mounted to jambs by riser type hinges which lift the door when it is swung open, and which use gravity to assist in the closing of the door. These hinges have two barrels mounted one above the other. Each barrel has a mounting flange laterally extending therefrom. The flange of one barrel is secured to the door and the flange of the other barrel is secured to the jamb.
A riser hinge is a hinge which incorporates a means for raising the door as it is swung open. Typically this is in the form of a camming arrangement in which the barrel of the hinge mounted to the door rides up a camming surface as the door swings open, thereby lifting the door. This feature is desirable for several reasons. One reason for such is that as the door is swung open the clearance between the bottom of the door and the floor is increased, so that door operation is not hindered by small objects resting on the floor or floor variances in its path. The problem of floor clearance is important where the refrigerator floor and the adjoining floor are at the same level since to assure a good seal the door must fit tightly against the floor when fully closed, yet have ample clearance when being swung open. This lifting also prevents the wearing of a bottom gasket mounted to the door which seals the door when closed. Lastly, once the camming system has been actuated by opening the door, the door may be automatically closed upon being let go, with the weight of the door itself actuating the camming system in the reverse direction, if the camming system is not positioned at a resting or dwell position.
A problem long associated with this type of hinge when used on very heavy refrigerated room doors is that they typically do not lift the door fast enough to avoid irregularities in the floor. This problem is caused because the cam lifting configuration does not provide enough lifting force and is limited by the amount of bearing contact surface on the cam. If the bearing contact surface is insufficient the plastic cam material will cold flow resulting in damage and a short service life.
It thus is seen that a need remains for a heavy duty riser hinge which alleviates problems associated with those of the prior art. It is to the provision of such therefore that the present invention is primarily directed.